System and apparatus for flowing wells



Aug. 6, 1946. A D NlXON. ,459-3 SYSTEM AND APPARATUS FOR FLOWING WELLSFiled June 29, 1944 I 2 sheets-Sheet 1 wam/tov Aug., a, w46. J; D, NIXON2,405,323

SYSTEM AND APPARATUS FOR FLOWING WELLS l .Filed June 29, V1944 2sheets-sheet z Patented Aug. 6, 1946 SYSTEM AND APPARATUS FOR FLOWINGWELLS `leddy D. Nixon, New Braunfels, Tex.

Application June 29, 1944, Serial No. 544,397

(c1. a-23s) 18 Claims. 1 This invention relates to new and usefulimprovements in systems and apparatuses for flowing wells.

In producing wells by the gas lift method wherein mechanically oper-atedmeans and/or automatically operated or pressure differential i means areemployed, there are certain occurrences and operating phases whichpresent fluid lifting problems, as well as requiring considerable manualsupervision. These occurrences are dueprimarily to a number of factors.Oil and gas wells vary considerably in their rate of flow, as

well as in producing characteristics and therefore,V the ow of any givenowing well is more or less unstable. Further, where a head of liftingfluid is carried kin the casing or annular space surrounding the tubing,the pressure is subject to wide variations, ranging from a completeshutv ofi to pressure drops which may be of small consequence, or whichmay fall below the working pressure, required to lift the column or headof well uid accumulated in the tubing, above the point of entry of thelifting uid.

Where intermittent lifting is installed, it is customary, in somesystems, to carry the lifting fluid in the casing, under a substantiallypredetermined pressure which, when said lifting fluid is admitted to thetubing, will be sufficient to lift the column of well fluid (above thepoint of admission) to the surface. of the column of well iiuid, or thehydrostatic load together with the lifting velocity it is necessary tomaintain, must be estimated, so that under normal production flowssatisfactory lifting and delivery of the well fluid is obtained.

The column of well fluid may rise above the optimum working level in thetubing from different causes. One instance is where the supply oflifting pressure fluid is shut off eitherY intentionally orunintentionally; another, where the pressure of the lifting fluid-storedunder a head pressure in the casing or annular space, drops sufficientlyto make it inadequate. In either case the column of well fluid will risein the tubing to the point where it must be kicked off from higherelevations or where lifting iluid at additional pressure must beadmitted at substantially the same elevation in order to elevate vtheincreased load.

Another instance would be where the normal or 5' predetermined amount oflifting fluid was being admitted to the tubing and the well headed thusincreasing the hydrostatic load beyond the capacity of the admittedlifting fluid to carry the v However, the height 2 load of well fluid tothe top of the well and deliver it or inadequately elevate such wellfluid.

In the devices set forth in my Patent No, 2,204,- 817, a mechanicallyoperated valve was located at the point down in the well where thelifting fluid is admitted under predetermined well flowing. conditions;and at higher elevations automatic or pressure differential valves weremounted, in upwardly spaced order. rllhe automatic valves would openunder pressure differentials, but being at a higher elevation than themechanically operated valve, they did not co-act therewith.l For thisreason the well could only be produced at one level with themechanically operated valve, and due to the many different producingcharacteristics of all wells, it was difficult to predetermine the mostfavorable location for the mechanical operated valve.

One object of the invention is to provide an improved system of 'flowingwells wherein a head of pressure fluid is carried in the casing andValve means are provided, whereby surface-controlled mechanical'admission of the pressurefluid to the tubing, may be periodicallyperformed to lift fluid in the tubing, and additional pressure nuid maybe automatically admitted to the tubing, to maintain lifting efficiencywhen the load so requires.

An important object of the invention is to provide an improved flow unitadapted to be connected in the tubing and including both a mechanicallyoperated pressure-fluid inlet valve and an automatic pressure fluidinlet Valve, arranged to operate in conjunction or independently;wherebythe quantity of pressure uid admitted to the tubing may be variedin accordance with `the load of fluid to be lifted and also, whereby thewell may be kicked 01T with a reduced amount of manual manipulation andsupervision.

A further object of the invention is to provide a unit of the characterdescribed, whereby both a mechanically operated pressure fluid inletvalve and an automatic pressure fluid inlet valve may be mounted in thetubing at substantially the samev elevation, and also whereby, thenumber of connections in the tubing may be reduced, over the use ofseparate valve housings and the number of thread hazards lowered. f

Still another object of the invention is to provide a unit of thecharacter described wherein the opening of the mechanically operatedValve causesl the pressure in the tubing to build up, thereby causing,the automatic valve to open and admit additional pressure iluid when theload to be lifted requires such additional energy.

lA further object of the invention is to provide s an automatic valvewhich may operate independently as a kick-off valve and which includes,resilient means, acting once the valve is open, to hold it open;together with means for controlling the inlet Velocity of the pressureduid and means for causing the valve to close with a snap action.

A construction designed to carry out the invention will be hereinafterdescribed together with other features of the invention.

The invention will be more readily understood from a reading of thefollowing specification and by reference to the accompanying drawings,wherein an example of the invention is shown, and wherein:

Fig. 1 is a view partly in section and partly in elevation, illustratinggenerally, a system and apparatus constructed in accordance with theinvention,

Fig. 2 is an enlarged transverse, vertical sectional view of one of theunits and showing the valve operating bar in engagement with one of themechanical valves to open the same,

Fig. 3 is an enlarged horizontal cross-sectional view taken on the line3-3 of Fig. 2,

Fig. 4 is an enlarged horizontal cross-sectional view taken on the line4-4 of Fig. 2,

Fig. 5 is an enlarged horizontal cross-sectional view taken n the line 55 of Fig. 2, Y

Fig. 6 is an enlarged sectional View of the valve bushing.

In the drawings, the numeral Ill designates the usual well casing havinga casing 0r tubingV head II at its upper end which supports the tubingI2 in the usual manner. The headis suitably connected to the upper endof the casing to close the same, and is suitably packed o around thetubing so that pressure fluid may be trapped or introduced into thecasing, thereby providing a head of pressure fluid in the casingavailable for im mediate admission tothe tubing under a predeterminedpressure. The casing I0 may have the usual perforated liner or strainerI3, at its lower end and the lower end of the tubing may be equippedwith a bull plug strainer I4 and a standing valve (not shown) as iscustomary in this art. In order to prevent the pressure fluid owing downto the producing formation and also, to provide a more eiicient trappingof the pressure fluid, a suitable packer I may be disposed between thecasing I0 and the tubing I 2 at the proper elevation; however, in someinst-allations the packer could be omitted.

In the string of tubing I2 one or more elongated dow units l5 areconnected. The number and spacing of the flow units, at differentelevations, depends on the conditions of circumstances surrounding'eachindividual well installation, as well as the use or requirement of anyother flow equipment used therewith. Under some conditions it might bepreferable to employ only one ow unit IG located below the standinglevel of the fluid in the well at the desired distance therefrom,

Each valve unit includes a cylindrical housing I1 having an axial boreI8 connecting internally screw-threaded boxes I9 at each end of thehousing. These boxes are of the type in common use in the oil fields andreceive the screw-thread ed ends (notV shown) of the sections of tubingI2. At one side of the bore spaced vertical iiow ducts 2B open to thebore IB, extend from one box to the other box. At the central portion ofthe housing a pair of vertically spaced annular recesses 2| are providedin the Vouter surface and each recess is provided with an axialscrew-threaded bore 22 extending radially of the housing to thevertically bore I8 thereof.

A bushing 23 is screwed into each radial bore 22 so that its inner endis substantially flush with the housing bore I8. Each bushing has anintegral collar or head 24, received in the recess, but less in diameterthan said recess. The head 24 may be provided with wrench faces (notshown) for receiving a socket wrench whereby the bushing may be radiallyscrewed into the bore 22. The bushings are of particular constructionbut a description of one bushing with itsI coacting elements willsuffice for both.

As shown in the enlarged View (Fig. 6) the bushing has an axial duct orpassage 25 which is provided at its outer end with screw threads 25 forreceiving a flanged retaining nut 2'?, which has a central port 28. Theinner end of the duct is reduced to provide an annular seat 29. A valveball 3i! is coniined in the duct between the nut 21 and the seat 2t. Theball is of such size as to engage the seat and close the duct as well asto move freely from the seat and provide sufficient clearance for apressure fluid, entering through the port 28, to Icy-pass said ball andflow into the bore I8 of the housing. When the ball is seated, (by thepressure fluid from the casing) a portion of its surface will protrudeinto the bore I8, whereby the beveled end 3| of a weight bar 32 mayengage said ball and displace it from its seat; the ball being held @ifits seat by the cylindrical surface of said bar. There may be suincientclearance between the bar 32 and the wall of the bore It to permit fluidto by-pass; howover, the vertical iiow ducts 20 are provided to permit afree upward iiow of fluids and liquids.

The bushing 23 and its ball 3c constitute a mechanically operated valve,which will be referred to generally as A and, as hereinafter described,the valve is opened by the bar 32 and closed by the velocity of thepressure fluid ilowing through the duct 25. In order to protect thevalves and prevent obstructive matter entering the same, a perforatedscreen or guard 33 is provided. The guard is curved transversely on anarc conforming to the surface of the housingF which is milled out at 34,to receive said guard, so that its outer surface lies ush with thesurface of the guard. The housing may be suitably fastened in place, asby machine screws St (Fig. 3).

By making a chordal cut across the side of the 'housing opposite thevalves A, a vertical recess 36 is provided for an automatic valve B. Thevalve B includes a transverse plate 3'! having integral with its centralportion a vertical valve casing 38. The plate 3'! is removably fastenedin the recess 35 by machine bolts 39 on each side of the casing and hasits vertical edges terminating fush with the surface of the housing I8and finished to conform to the housing contour. The vertical edges ofthe guard 33 abut the projecting edge portions of the plate 31, wherebya smooth joint is formed. The outer face of the casing 3B is curvedtransversely to conform to the contour of the housing. The casing isbored and counterbored axially, to form an upper fluid receiving chamber40, the top of which is closed by a plug 4I countersunk in the top ofthe casing.

Below the chamber 43, the casing 58 is counterbored to form a pistoncylinder 42, below which the casini?,r is further counterbored to form asump 43 having a valve seat 44 at its lower end. An axial duct 45extends from the seat to a point adjacent the bottom of the casing. Acounterbored lateral 45 extends from the inner side of theA casing tothe bore 45 and communicates with its port 4l extending through the wallof the housing and providing communication with the bore I8 thereof. Aflanged bushing 48 Vis driven in to the lateral 46 and is provided witha central duct `49. This bushing is an important element -because thediameter of the duct 49, is one means for controlling the velocity ofthe iiow into the housing bore I8, and by substituting bushings withbores of different sizes the velocity of ow through the bushing may bevaried, as will be hereinafter described.

A tubular piston 50 is disposed to reciprocate vertically in thecylinder v42 and sump 43. This piston is provided with a head 5 I at itsupper end having a close sliding fit in the upper end of the cylinder. Acoiled spring 5'2 surrounds the piston in the cylinder and is confinedbetween the head 5I and a anged collar 53 resting on the bottom of thecylinder, as is clearly shown in Fig. 2. The lower end of the piston 55is tapered as shown at 54, to engage the seat 4d and shut off Iiow offluid to the duct i5 and also to the bore I8 of the housing II. Amanifold 55 extends from the top of the tubular piston axially down intothe head 5I, and has a plurality of upwardly inclined spaced ports 55extending radially therefrom through the head to the outer surfacethereof. When the piston 50 is seated these ports are closed by the wallof the cylinder, but when the piston is moved upwardly, these ports areexposed in the chamber 4I). For limit ing the upward movement of thepiston, an adjusting screw 5l mounted in the plug 4I, is set to beengaged by a cap screw 53 which is screwed into the upper end of themanifold 155 and closes the upper end of the same. By adjusting thescrew and limiting the upward stroke of the piston, the areas of theports 5S exposed in the chamber 40, may be varied and controlled.

As hereinbefore stated the housing is connected in the tubing I2 and ahead of pressure fluid is carried in the casing IIJ above the packer I5.Gas which is usually available in oil elds may be employed as thepressure uid and such gas is forced into the casing so that a workingpressure is built up in the casing, suitable to lift a load or column ofliquid standing in the tubing above the point of admission. The wellconditions, of course, control the degree lof pressure, however, workingpressures of from 300 to 500 pounds per sq. in. have been foundsatisfactory. Of course, air or any other kind of pressure fluid may beemployed. To properly admit the pressure fluid to the chamber 4B, theouter wall thereof is provided with perforations 58 which act as astrainer to keep out foreign matter. When' the piston 50 is elevated toexpose the ports 55, the pressure fluid which constantly fills thechamber 40, will be admitted to the manifold 55, wherebiT it may owthrough the bore of the piston, downwardly thereof. v

Intermediate its ends, the piston is provided with a plurality of smallports 59 which are so located as to always discharge into the cylinder42. These ports admit pressure fluid to the cylinder so that when theports 56 are open, pressure is equalized above and below the head 5I. Atthe lower end, the piston is provided with a plurality of ports Eilwhich discharge into the sump 43, thus permitting flow into the duct 45when the piston is unseated. The pressure uid flows from the duct 45through the duct 49 of the bushing 46 and thence through the port 41into the bore I8 of the casing I'I. When the piston 50 is in its closedposition as shown in Fig. 2, the spring 52 will be under apredeterminedcompression but will not exert enough expansive force to move the pistonupwardly so long as its tapered end -54 is in engagement with the seat44 and the ports 56 are closed, because the uid pressure exerted on theupper end of the piston in the chamber 4G will be greater than thisexpansion force.

It is obvious that when the column of liquid 'rises in the bore I8 ofthe housing, that back pressure will be exerted through the port 4l,duct 49 and duct 45 against the exposed area of the lower end of thepiston. When the back pressure coupled with the expansive force of thespring is sufficient to overcome the pressure fluid acting on the upperend of the piston 55, the piston will be moved upwardly thereby exposingthe ports 56 in the chamber 4B and opening the valve B. Pressure fluidwill be admitted through the ports 55 and discharged through the ports50 into the duct 45, from whence it will ow through the duct 49 and port4l into the bore I 8, and provide a lifting fluid for the column ofliquid standing thereabove in the bore I8. The spring 52 acts to holdthe piston 5t) open, once the ports 55 are exposed. When flow conditionsreach the point where a predetermined velocity of flow through the duct43 is attained, the flow of the pressure fluid through the piston willinitially move .the same downward until. the ports 56 are closed,thereafter the pressure fluid will act directly upon the upper end ofthe piston, thus seating it with a snap action.

It is pointed out that the closing of the automatic valvermay becontrolled through the ports 56 instead of through the port 49 of thebushing 4S. It is obvious that when the head 5I of the piston has moveddownwardly into the bore 42 sufficiently to partially close said ports,the flow therethrough will be restricted and the velocity stepped up,whereby the valve will be closed with a snap action.

The weight bar 32 is suspended on a wire line 6I and is operated in amanner, fully described in Nixon Patents 2,204,817 and 2,171,478. Whenthe well is shut down, the weight bar may be in the position sho-wn inFig, 2, with respect to the lowermost unit, hereinafter referred to asC, or it may be raised to the top of the tubing above the uppermost unitI5, hereinafter referred to as E.

Under normal or regular'operation, one unit I5 is connected in thetubing at a depth or elevation, above which elevation, the column offluid to be lifted, is accumulated; and this unit may be referred to asthe regular or normal flowing unit C. If more than one unit I6 isconnected in the tubing at higher spaced elevations, the regular unit Cis lowermost. Usually several units I5 will be installed, but for thepurpose of illustration only three such units C, D and E are shown inFig. l. The number of units will depend upon the particular wellinstallation. The reason for this is manifold because it permits theweight bar 32 to be successively lowered through the units` nui-.i whenthe weight bar is inoperative at the lowerrnost unit, to kick 01T thewell, when the column of well fluid builds up in the tubing. Also,whenever the valves A are opened at any given elevation, automaticvalves-'B at .substantially the `same elevation may yopen toautomatically vassist in lifting thecolumn of wellfluid or a slugthereof. Also the automatic valvein each unit may `open whether themechanical valve is open or closed. Y

As before stated, Ithe yunit i' .may be operated under various wellconditions. When the well fluid is being produced under regular flowing,as hereinbefore set forth, vthe -bar 32 will be moved upwardly in thebore I8 of unit C to `unseat the ball 30 and admit a predeterminedquantity of lifting uid. The lifting -fluid admitted may or Vmay not besuiicient 4to raise to the surface and discharge, the column of wellfluid, usually accumulated above the Vvalves r'l.

The opening of the automatic valves B is controlled entire-ly bypressure differentials thereacross. When the pressure of the liftingfluid from the casing H3, predominates, the automatic valves will beclosed. However, when the pressure of the hydrostatic load of liquid inthe tubing l2, plus the expansive force of the spring 52,

creates a su-flicient pressure differential, the

automatic valve will open, Thus, if such `hydrostatic pressuredifferential is sufiicient, the automatic valves lbelow the liquid levelwill be open kand the automatic valves above said liquid level will beclosed.v

When flow from the tubing is cut off, as by a valve '52, .the automa-ticvalves cease to function to lift liquid.v Also, when the well is shutoff the automatic valves below the liquid level in 4the tubing are open,liquid will flow therethrough linto the casing, thus establishing liquidlevels in both the tubing and the casing.

The auxiliary supply of lifting fluid is ventirely automatic and beingadmitted at substantially the same elevation :as the mechanicallyadmitted iiuidis of great advantage in'maintaining a stabiliaed liftingof the well fluid. Further, the valves B will automatically close whenthe proper upward now or discharge of well fluid is attained. The ball39 is velocity-seated as described in my Patent No. 2,171,480. As a headof .gas is carried in 'the vwell casing 2l, such stored gas is carriedunder sufficient pressure to compensate the pressure drop when gas isadmitted to the tubing so that the gas admitted to the tubing While thevalves are open will be under suflicient Working pressure to adequatelylift the rslug or column of well uld.

Should for some reason the supply of .gas to the well casingA be cut oi,or drop below the .necessary working pressure, the column of well fluidin the tubing would build up. This occurrence would be in the nature ofan emergency and would be somewhat controlled by the amount and durationof the gas-pressure failure and the rate at which the well built up itscolumn of luid.V Assuming that the bar 32 was resting adjacent and belowthe regular flow uni-t C, at this time, and gas pressure was restored,then when the bar 32 was moved to open the valve A, the valves B wouldalso be automatically opened and. supply additional gas to lift theload. If additional units I3 were installed above the regular unit C,the valves B thereof would open according to the pressure differentialsat the same, and unload the well.

When ya Well is intentionally shut down by closing valve 62 and cuttingolf the supply of pressure fluid, as under iproration laws, .the columnof liquid will build up in the tubing to its highest standing level.When it is desired to .star-t owing the well by a :gas lift, it isnecessary to kick off the well, whereby the level ofthe well liquid islowered to a working level, where 'theregular column of Well liquidusually stands, when operation from the lowermost unit C is performed.Under such kicking oir" or unloading, the weight bar 32 having been.raised to the top of the well, is lowered into the first -or uppermostun-it E to open the valves A thereof -to admit lifting fluid, `and thendown to the next valve unit D, and so on until'the lowermost unit 4isreached. This, however, is a mechanical operation and .requires manualmanipulation and supervision.

It is one Vof the features =of this invention to provide the valves Bfor automatically kicking volf the well, thus obviating manual manipula'tion and supervision. When `a well is shut down, the supply of pressurehuid to the casing `Ill is cut off so that the pressure ln the casingdeclines or it may be suitably vented to the atmosphere.

The uppermost unit Eis, of course, 'connected in the tubing, usually avsuitable distance below the high level to which the liquid will risetherein when the well is lshut for a period of hours'or days; however,the liquid -m-aynot rise to the uppermost valve E.

When .the fluid pressure in the casing l0 reduces and the liquid risesin said casing, as herein before described; the spring 572 of `any valveB above the liquid level in the casing, will for-ce the piston 50upwardly and thus open the val-ve; while the hydrostatic load in thetubing and the springs 52, will force open all valves B, belowthe liquidlevel in the casing. To start the well flowing, that is to kick it off,pressure uid is again supplied to the casing to build up the pressuretherein and the valve 4li? iis-opened. Any valve B Alocated above theliquid levels Will be closed by the pressure fluid.

As the pressure .fluid builds up in the casi-ng the liquid level thereinwill be depressed and the liquid from the casing forced-back into thetubing through the immersed vvalvesl `B until the lautomatic valve ofunit D is reached. When this occurs the level in the tubing will havebeen raised above unit D, and therefore pressure fluid will enterthrough the automatic valve of lunit D and start the liquid thereabovein the tubing, flowing upwardly. This operation will be repeated Vateach succeeding lower unit until Yregular flow is established. The wellis thus automatioally kicked oif. Of course, when the velocity flowthrough any automatic valve reaches the kpredetermined point, such valvewill be automatically closed.

It may `occur that it is desired to mechanically kick off the well andin such case, the weight bar 32 would have been raised to the top of thetubing. The weight bar 32 is lowered to unseat the valves 30 vo-f therst immersed unit, merely passing through the units thereabove. Whenthis occurs the automatic valve .of such unit W-ill also open, but asthe hydrostatic load inthe tubing at this first immersed unit, may berelatively low, said automatic valve would probably not remain open forits usual period of time, particularly when `both the Valves A and B areopen.

It is Pointed out that Aafter a slug or column of liquid being lifted,passes any automatic valve, the hydrostatic load plus the expansiveYforceof the spring 52, will cause the valve to open and admitadditional lifting iiuid to the tubing. This arrangement has manyadvantages Vbecause an Vadequate supply of lifting fluid is assuredunder 9 all flowing conditions. Where the force exerted by the liftingfluid falls below the lifting requirements of the load; there is dangerof slippage of the slug being lifted. This term is applied where theslug of oil tends to slip down the tubing instead of being carriedupwardly therein. Oil and gas wells have a habit of unexpectedly flowingabnormally, which in the oil fields is called heading Heading of oilbrings into the tubing an abnormal amount of oil and causes the oillevel therein to rise above its working level. As

the automatic admitting of additional lifting fluid to the tubing iscontrolled almost entirely by the hydrostatic load of liquid in thetubing, it is obvious that when the Well is being operated mechanically,any additional liquid load is automatically handled. However, theautomatic valve is so collaborated that when the well is being regularlyoperated, the automatic valve will not open until after the slug orcolum of liquid being lifted has passed the port 49 of such valve. Thisprevents pressure fluid entering intermediate the ends of the slug andchanneling therethrough.

It is also to be observed that by providing the mechanically operatedvalves A in the units and also'the automatic valves B, either type ofoperation is available. Automatic valves are sub-ject to certainimperfections and sometimes' fail to work. Sanding up, clogging andspring breakage are some of the causes. If an automatic valve shouldfail to kick-off, the operator may raise or lower the Weight bar 32 andopen the necessary valves A, at the level where the trouble occurs. Whenthe well. is automatically kicked-off, the

weight bar 32 is usually maintained in its lowvered position at the unitC, where it is available for immediate operation. y

'Ihe general construction of the automatic valve B is important. Owingto the size of the piston 52 and the various passages and ports, thisvalve is not likely to clog up with sand. Also there are `no delicate orfinely balanced parts. The automatic valve is rugged as well as simple.The foregoing description of the invention is explanatory thereof andvarious changes in the size, shape and materials, as Well as in theAdetails of the illustrated construction may be made, Awithin the scopeof the appended claims, without departing from the spirit of theinvention.

What I claim and desire to secure by Letter Patent is:

l. The system of flowing a well having tubing therein receiving wellfluid flowing from the producing formation which includes, meansproviding a source of pressure uid outside of the tubing, means operablefrom the surface at the top of the well for controlling the admission ofpressure fluid to the tubing to lift a predetermined column ofwell fluidfrom a given elevation, means for automatically admitting additionalpressure fluid to the tubing at substantially said given elevation whenthe hydrostatic head of the well uid column sets up a predeterminedpressure differential to co-act with the first admitted liftting fluidto maintain continuous lifting of said 'f of the well for controllingthe admission of pressure fluid to the tubing to lift a predeterminedcolumn of well uid from a given elevation, meansv for" automaticallyadmitting additional pressure fluid to the tubing at substantially saidgiven elevation Vwhen the hydrostatic load of the well fluid column setsup a predominating pressure differential, but which is less in pressurethan the pressure of the lifting fluid to co-act with the rst admittedlifting fluid to maintain continuous lifting of said hydrostatic load,and means for automatically shutting olf the admission of suchadditional pressure fluid at said given elevation.

3. The system of flowing a well having tubing therein receiving wellfluid flowing from the producing formation which includes, meansproviding a source of' `pressure fluid outside the tubing, means formechanically and positively admitting pressure iiuid to the tubing tolift a load of liquid in the tubing from a given elevation, means foradmitting additional pressure fluid at substantially the same' elevationto assist in lifting increased loads, and means for automaticallyshutting off the admission of such additional pressure fluid when apredetermined velocity flow of such pressure fluid is reached.

4k; The system of flowing a well having tubing therein receiving wellfluid flowing from the producing formation which includes, meansproviding a source of pressure fluid outside the tubing, means formechanically and positively admitting pressure fluid to the tubing tolift a slug of liquid in the tubing, means for automatically admittingadditional pressure fluid to the tubing substantially opposite the pointof mechanical admission When the slug of liquid being lifted has passedthe point of admission of said additional lifting fluid, and means forshutting olf the admission of all lifting fluid when the slug of liquidreaches a predetermined point at the top of the well.

5. The system of flowing a well having tubing therein receiving wellfluid flowing from the producing formation which includes, meansproviding a source of pressure fluid outside the tubing, means formechanically Vand positively admitting pressure uid to the tubing tolift a slug of liquid in the tubing, means for automatically admittingadditional pressure fluid to the tubing substantially opposite the pointof mechanical admission when the slug of liquid being lifted has passedthe point of admission of said additional lifting fluid, and means forautomatically shutting off the admission of such additional pressurefluid when a predetermined velocity of such pressure fluid is reached.

6. The system of flowing a well having tubing therein receiving wellfluid flowing from the producing formation which includes meansproviding a source of pressure fluid outside the tubing, means forpositively admitting pressure fluid to the tubing, means forautomatically admitting additional pressure fluid to the tubing whilepositively admitting such pressure fluid at substantially the sameelevation to lift a load of liquid to the top of the tubing, and meansfor shutting off the dual admission of pressure fluid when the load ofliquid is elevated in the tubing.

'7. The system of flowing a well having tubing therein receiving wellfluid flowing from the producing formation which includes meansproviding a source of pressure fluid outside the tubing, means forpositively admitting pressure fluid to the tubing, means forautomatically admitting additional pressure .fluid at Substantially theSame elevation to the tubing while positively admitting such pressurefluid to lift a'load of liquid to the top of the tubing, and means forautomatically shutting off the dual admission of pressure fluid when theload of liquid is elevated in the tubing.

8. The system of flowing a well having tubing therein receiving wellfluid owing from the producing formation which includes means providinga sourceV of pressure 'fluid outside the tubing, means for positivelyadmitting pressure fluid to the tubing, means for automaticallyadmitting additional pressure iiuid to the tubing while positivelyadmitting suchY pressure' fluid atsubstantially the same elevation tolift a'load of liquid to the top of the tubing, and means forautomatically shutting off the admission of the automatically admittedpressure uid when a predetermined velocity flow thereof is reached.l

9. In combination, a Well tubing, and spaced units connected in'saidtubing,.each unit having a mechanically operated valve for admittingpressure duid and an automatically operated valve substantiallyVopposite the mechanically operated valve for automatically admittingpressure fluid.

l0. In combination, a Well tubing, and spaced units connected in saidtubing, each unit having a mechanically'operated valve for admittingpres'- sure fluid andan automatically orated valve substantiallyopposite the mechanically operated valve for automatically admittingpressure fluid, each valve having means for closing it when apredetermined flow of pressure uid therethrough is reached.

11. In combination, a well Casing carrying a head of pressure fluid, atubing in said casing having liquid standing therein, a 'plurality ofunits connected in spaced order insaid tubing, each including anenclosure connected at each end to the tubing having a mechanicalpressure.- fluid inlet valve, means movable through successive units andcontrollable'fiom the surface of the Well for openingv the mechanicalvalves, and an automatic pressure-fluid inlet valve carried in theenclosure of each unit adjacent the rnechanical valve.

1'2. A well-fluid lifting unit including, a housing having a fluidpassage therethrough, a mechanical pressure-iluid inlet valve having aportion exposed in said housing passage, means controlled from thesurface of the Well for engaging the exposed portion of the mechanicalvalve and opening the same, and an automatic pressure fluid inlet valvecarried in said housing and communieating with the iiuid passage thereofadjacent the mechanical valve.

13. A well-fluid lifting unit including, a housing having a pluralityofpressure uid inlet openings and a fioW passage communicatingl withsaid openings, a ball valve closing one of said openings, aspring-impelled valve closing the other opening, both of said valvesbeing adapted to Close under predetermined flow velocities thereacross.1

14. A Well-fluid lifting unit including,` a housing having a iiowpassage therethrough, a positively operable valve for admitting pressurefluid to said passage, and an automatic valve for kadmitting pressurefluid to said passage including resilient means for opening it andmeansl for causing the valve to close when a predeterminedvelocity nowtherethrough iS attained.

1,5. A ow unit for a Well for controlling the admission of a pressurelifting iiuid to a column of well uid during the varying rates of flowof the column including, a flow conductor adapted to be connected to theWell fluid ow line, `mechanically operated means for admitting pressurelifting fluid to the 110W conductor for lifting a column of well duidtherein, and automatically operated means substantially opposite themechanically operated means for admitting pressure lifting fluid to theflow conductor when the column of well fluid passesy said automaticallyoperated means.

16. An apparatus for flowing. oil Wells having a casing and tubingtherein which includes, means for trapping a volume of pressure fluid inthe casing, and means for admitting pressure iiuid tothe tubing in twostages at substantially opposite points including surface controlledelements for positively admitting pressure fluid to the tubing, from thecasing to lift a load of well fluid 'to the top of the well at a singleoperation and ing and having a Well fluid passage therethrough,

a mechanical valve in the enclosure opening to the passage adapted to bemechanically opened toy admit a predetermined volume of pressure liftingfluid, and an automatic valve in the enclosure opening to the passagesubstantially opposite tov the mechanicalvalve adapted to beautomatically opened by an excessive load of well 5o fluid after themechanical valve is opened.

18. A Well-fluid lifting unit including, -a housnghaving a plurality ofpressure fluid inlet openings and a well fluid flow passage-therethroughcommunicating Withsaid openings, a ball valve 53 closing one of saidopenings, a spring-impelled (5o the Well fluid load decreases to apredetermined value.

J EDDY D. NIXON.

